There is a current trend in medicine to minimize surgical and interventional procedures, concomitant with the development of minimally invasive tools to access, visualize, infuse, treat, medicate, sample, and interact with internal structures of the body. Occasionally, devices such as catheters, balloons or wires are inadvertently severed in a blood vessel, cavity or organ. Depending on location, the severed device or fragment may be retrieved. Frequently, a surgical approach is dangerous and costly. In many cases, access has already been established to the severed device, fragment, or foreign body in question, and it is just a matter of locating and removing the foreign body without doing harm to surrounding tissue or forcing it further out of reach.
Certain medical devices are known that are utilized in the ducts and vessels of a human or veterinary patient for retrieval of bodies from the patient. For example, retrieval devices are known for removing calculi such as kidney stones or gallstones from a patient, where the retrieval device is delivered to the target site via the urethra or biliary duct, respectively. The device's distal tip is adapted to deploy at the site to form a basket shape to trap the calculi after which the basket is collapsed to grasp the calculi. Both the device and the grasped calculi are then withdrawn from the patient.
One such stone retrieval device is disclosed in U.S. Pat. No. 5,989,266, in which several loops of wire are caused to emerge from the distal end of a sheath that has previously been delivered through the renal or biliary system of a patient to the site of the stone. The stone becomes trapped within the loops, after which the loops are pulled proximally mostly into the sheath, grasping the stone firmly, after which the sheath, loops and stone are withdrawn from the patient. The loops are disclosed to be made from a superelastic alloy such as nitinol to automatically form the loops when caused to emerge from the sheath's distal tip. Other similar stone retrieval devices are disclosed in U.S. Pat. Nos. 5,057,114; 5,064,428; 5,133,733 and 5,484,384.
However, use of such devices is not satisfactory for grasping such an object within the vascular system of a patient for repositioning of that object, or for removal of objects from within the vascular system of a patient. For example, in certain situations it is desired to reposition a stent or stent graft within the vasculature, or to retrieve or reposition a malpositioned or misplaced embolization coil. And during delivery and deployment of a bifurcated stent graft at the site of an abdominal aortic aneurysm when surgical access has been obtained through the femoral arteries on both sides of the groin, it is desirable to grasp the distal tip of a guide wire extending into the aneurysm from the contralateral iliac artery, to be pulled into the ipsilateral iliac artery at the vessel's aorto-iliac bifurcation, for eventual placement of the contralateral leg extension of the stent graft.
For vascular use, another known device is a suture loop on a catheter distal tip. Yet another is a guide wire that has been doubled over and extended through a catheter so that its distal end forms into a loop that extends axially from the catheter's distal end to be utilized as a retriever when it is pulled proximally to capture an object and hold it against the catheter distal end for withdrawal, sold as the Curry Intravascular Retriever Set by Cook, Incorporated, Bloomington, Ind. A version of the stone basket device, having helical loops, has been utilized for intravascular retrieval, the Dotter Intravascular Retriever Set also sold by Cook, Incorporated.
U.S. Pat. No. 5,171,233 discloses a snare-type probe for intravascular use. After a catheter is inserted into the patient's vascular system to the site of the foreign object, an elongate member having a loop-shaped distal segment is inserted into the proximal end of the catheter's lumen until the loop-shaped distal segment emerges from the catheter's distal tip at the site. Then the loop-shaped segment extends at an angle to the adjacent portion of the member and opens into a loop. Once a free end of the foreign object is snared within the loop-shaped distal segment as determined by fluoroscopic equipment, the loop-shaped distal segment is pulled proximally into the catheter distal end, collapsing about the ensnared foreign body fragment and holding the foreign body at the distal tip of the catheter during withdrawal. The elongate member is preferably disposed within an outer sheath and is disclosed to be one wire, or two gripped-together wires, of a shape memory material such as a superelastic nitinol alloy, with a single preformed loop shape at the distal segment defined by two wire portions. The use of nitinol enables the wire segments defining the distal segment to be straightened and collapsed upon one another into an elastically deformed configuration to pass through the lumen of the catheter and yet automatically open into a loop and extend at a substantial angle upon emerging from the catheter distal tip. One characteristic of this design is that during retraction after grasping, the loop quickly changes, or “flips,” between the angled orientation and a generally axial one. This results in less assured control over the item during grasping, and may result in escape of the item, requiring redeployment of the loop for another grasping attempt.
Additionally, much of the prior art involving retrieval and/or repositioning devices and procedures does not protect against distal embolization which may occur during these procedures. This is a serious problem with potentially devastating effects. For instance, small plaque particles less than 200 microns, which may be dislodged during a retrieval and/or repositioning procedure, may cause neuronal ischemia, and periprocedural microemboli resulting from such a procedure may cause stroke or neurologic dysfunction. In fact, procedures such as carotid angioplasty and stenting have been shown to have a perioperative stroke rate of more than 3%, largely due to emboli.
It is desired to provide a medical grasping device for grasping and repositioning an object within the vascular system of a patient, such as a stent or stent graft or embolization coil or such as the distal tip of a catheter or a guide wire; or to grasp a stent or embolization coil, or a fragment from a catheter or guide wire or a pacemaker lead, for its removal from the patient.
It is also desired to provide a low profile, medical grasping device that is conformable to the vascular anatomy while generating a substantial tensile force.
It is further desired to provide such a device that is trackable through the vascular system over a guide wire already in situ.
It is yet further desired to provide such a device that is atraumatic to the patient.
It is also further desired to provide such a device that protects against distal embolization which may occur during a retrieval and/or repositioning procedure.